An optical fiber including fiber Bragg gratings can be used as a sensor fiber to detect temperature, strain and/or torsion. Such sensor fibers are used to control materials and processes. By inscribing fiber Bragg gratings (FBG) in the fiber core, a sensitivity with respect to changes in temperature and/or length is achieved. By a combination of some fibers of this kind, it is possible to detect bending and tension of materials. To reduce environmental effects, single FBG are included in one fiber which contains more FBG.
Information relevant to producing multi core fibers can be found in U.S. Pat. No. 5,563,967. This patent discloses a method for the production of a sensor fiber with two FBG cores. Such sensor fibers allow for the simultaneous detection of temperature and length changes.
The sensor fibers known in conventional art bear the disadvantage that it is not possible without further processing to detect changes of length, bending, temperature and torsion. For the accumulation of extensive measurement data, many FBG are necessary and the analysis of the accumulated raw data grows more and more complex.
For the foregoing reasons, there is a need for sensor fibers able to sense with fewer FBG.